Knock out structure



D. DANIELS KNOCK OUT STRUCTURE Filed May 14, 1962 F 6 INVENTOR.

DENNIS DANIELS AT TORN YS United States Patent 3,152,715 KNGCK OUT STRUCTURE Dennis Daniels, Williarnsville, N.Y., assignor to Houdaille Industries, Inc Bulfalo, N.Y., a corporation of Michigan Filed May 14, 1962, Ser. No. 194,487 14 Claims. (Cl. 220-27) This invention relates generally to knock-out structures, and more specifically to structural details by which various advantages are obtained over prior art forms.

Although the principles of the present invention may be included in various devices, a particularly useful application is made in electrical wiring boxes of the type that are provided with a plurality of knock-out structures of various sizes which may selectively be removed to provide an aperture in the wiring box of a size appropriate to receive conduit fitting parts.

Certain prior art forms, when removed or knocked out leave a hole or aperture in the sheet-like box of the wall which is not absolutely round or smooth throughout the extent of the hole periphery. Further, certain prior art forms include a small non-severed portion which is integral with both the knock-out slug and the sheet material. Not only does the rupturing of such an integral connection leave an imperfect hole, but the same constitutes a source of extreme variation in removal force required, particularly where the structure is provided in a range of materials having a varying degree of toughness.

The present invention contemplates the utilization of a knock-out structure which incorporates a completely peripherally severed slug associated with an undulating means which, in a preferred embodiment, enables release of a selected portion of a plurality of concentric portions of the knock-out structure whereby a hole of selected size is readily obtained in the sheet making up the cabinet or box having the same.

Accordingly, it is an object of the present invention to provide an improved knock-out structure.

l Another object of the present invention is to provide a knock-out structure which, when opened, leaves a truly round or flash-free edge.

Yet another object of the present invention is to provide a knock-out structure which may be used in a plurality of materials having different strengths, the opening force of the structure being substantially constant as between such diiierent materials.

A still further object of the present invention is to provide a knock-out structure which may be selectively opened to a plurality of hole sizes arranged within each other.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheet of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

On the drawings:

FIGURE 1 is a perspective view of a knock-out structure provided in accordance with the principles of the present invention in a fragmentarily illustrated sheet of material;

FIGURE 2 is a plan view of the structure of FIG- URE 1;

FIGURE 3 is an enlarged cross-sectional view taken along the arcuate line IIIIII of FIGURE 2; and

FIGURES 4, 5, and 6 are plan views of modifications and variations of the structure shown in FIGURE 1.

i As shown on the drawings: The principles of this invention are particularly useful when embodied in a knock-out structure such as illustrated in FIGURE 1, generally indicated by the numeral 7 10. The knock-out structure 10 is formed in a sheet of material 11, such as of steel, which forms a part of an electrical wiring box, cabinet, switch housing, or the like, through which conduited wiring is to be passed. The knock-out structure 10 includes a central disc or slug 12, here illustrated as being flat and disposed coplanarly with the sheet 11. The knock-out structure 10 further includes an undulated annular member or slug generally indicated at 13, the inner periphery of which is defined by a continuous line of severance 14, and the outer periphery of which is also defined by a continuous line of severance 15. The undulated member 13 includes a series of undulations 16-21, the undulations 16, 18, and 2t protruding upwardly from the illustrated side of the sheet, and the undulations 17, 19, and 21 being depressed from the illustrated side of the sheet 11 so that they protrude from the opposite or lower side of the sheet 11.

In a preferred form, the disc 12 and the annular member 13 originally constituted an integral portion of the sheet 11 disposed where presently illustrated. It is thus apparent that the sheet 11, the disc 12, and the annular member 13 are all of the same thickness.

As best seen in FIGURE 3, the raised undulations 16, 18, and 20 protrude from the disc 12 and sheet 11 by an amount less than the thickness of the sheet, and similarly, the other undulations 1'7, 19, and 21 protrude in the opposite direction by an amount less than the thickness of the sheet.

As best seen in FIGURE 1, each of the undulations 16-21 comprises a flat central portion which extends parallel to the sheet 11, and each central portion thereof has end portions which extend into the sheet 11 as indicated at 12a and 19b in FIGURE 3, and which are respectively integral with an end portion 20a and 18a of the oppositely protruding adjacent undulations 20 and 18. It is to be understood that each line of severance 14 and 15 is in no sense interrupted adjacent to the various end portions of the various undulations so that if the disc 12 or annular member 13 be removed, there is defined at the line of severance 14 or 15 a truly round or flash-free opening.

As best seen in FIGURE 1, the undulations 16, 18, and 20 have a combined arcuate length which is somewhat greater than that of the undulations 17,19, and 21.

The outside diameter of the disc 12 at the severance line 14 and the inside diameter of the annular member 13 are nominally the same since the disc 12 was stamped therefrom. Since the severance line 14 is continual, a relative axial displacement is needed between every point on the annular member 13 and the disc 12. Thereafter,

' the disc 12 is restored to a coplanar relation with the sheet 11. The fit between the disc 12 and the annular member 13 which thus results has been for convenience herein termed as a press fit, and it is intended that such terminology should include such degree of interference as might result due to the forming of the undulations in the annular member 13. The outside diameter of the annular member 13 and the inside diameter in the sheet 11 at the severance line 15 has a fit which similarly is produced by pressing the annular member 13 to a central position, it likewise'being necessary to displace the same from its original plane around its entire periphery to obtain a complete severance at the severance line 15.

i If the disc 12 is struck from the illustrated side, as by a sharp blow from a hammer, it will readily pop out of the annular member 13. If the disc 12 is struck with a sharp blow from the opposite side, the disc 12 and the annular member 13 will pop out of the sheet 11 as a single unit. Thus a smaller hole is obtained when the structure 10 is struck from one side, and a larger hole is obtained when it is struck from the opposite side. This difference in response is due to the fact that the combined arcuate lengths of one group of undulations is greater than the combined arcuate lengths of the oppositely directed group of undulations.

The foregoing may be explained in greater detail as follows. The amount of downward force needed to force 'an angular increment of the undulation 20 through the sheet 11 is somewhat greater than the corresponding force is for the increment 19 since the undulation 20 would have approximately one and one-half thicknesses of relative movement, while the increment in the undulation 19 would have only approximately a half a thickness of the sheet of movement. Thus, the undulations 16, 18, and 20 would resist such movement to a greater extent due to the amount they must travel than would the undulations 17, 19, and 21. Further, the effective lengths of the undulations 16, 18 and 28 are greater than the effective lengths of the undulations 1'7, 19, and 21 so that the effect is emphasized. This relationship applies to the resistance to movement at the inner line of severance as well, whereby a reverse result is obtained. The high friction portion of the disc 12 is thus divided between the undulations 1'7, 19, and 21, but the arcuate extent thereof at the line of severance 14 is somewhat less than the arcuate extent at the severance line 15. Stated otherwise, there is a greater percentage of the periphery of the disc 12 disposed adjacent to low travel points of engagement at the undulations 16, 18, and 211 than that of the annular member 13 disposed at 17, 19, and 21. Thus, there is somewhat less resistance to movement at the severance line 14 than there is at the severance line 15 when the force is applied from above as shown in FIGURE 1. Conversely, the reverse is true when the force is applied to the disc 12 from the opposite side.

I have found that this structure enables the provision of a lower removal force than that required by prior structures, and paradoxically, if the disc 12 is removed, the annular member 13 will withstand a higher steady force than has been withstood by prior known structures, as may be applied by or through electrical fittings associated therewith. While this relationship is true without any electrical fitting disposed therein, the ability of the annular member 13 to withstand a removal force is accented or increased when clamping nuts or the like are tightened against the same. This produces a slight spreading action or tension which increases the static friction between the sheet 11 and the annular member 13 at the severance line 15.

Since the friction at the severance lines holds the parts assembled, the differences due to the removal force needed to break an integral connection such as employed in prior art devices employing materials of varying toughness is entirely eliminated. Moreover, the instant structure is inherently stable, and devices provided with the knock-out structure can withstand substantially any amount of dropping or hanging, the knock-out structure opening up only when given a direct blow. Stated otherwise, a hard blow delivered to the sheet 11, or a sudden arresting of its movement, will by inertia not cause either the disc 12 or the annular member 13 to pop out.

A simplified form of the invention is shown in FIG- URE 4 which includes a disc 22 having undulated annular means generally indicated at 23 extending around the disc 22 and integral therewith, there being a radius at the line indicated by the numeral 24. The outer periphery of the undulated portion 23 is defined by one continuous severance line 25. In this embodiment, the disc 22 is flat and is coplanar with the sheet 11. The undulated annular means 23 includes a pair of undulations 26, 27 which extend above the sheet 11 as illustrated,

' and a pair of undulations 28, 29 which protrude from the opposite side of the sheet 11. The combined arcuate lengths of the undulations 28 and 29 is substantially equal to the combined arcuate lengths of the undulations 26 and 27. Since this symmetry is present, a sharp blow of equal intensity delivered from either side will remove the disc 22. The fit between the disc 22 and the sheet 11 at the severance line 25 is again very tight and corresponds to the fit at the severance line 15 described above. The undulations 26-29, like the undulations 16-21, each include a flat central portion extending parallel to the sheet 11, and end portions each extending into the sheet and integral with an end portion of the oppositely protruding adjacent undulation. The amount of the protrusion in this embodiment is not critical, however, it is preferred that the protrusion be less than the sheet thickness so that the resulting structure, when not used as a knock-out structure, leaves the sheet 11 completely closed, as do all of the structures illustrated herein. It is evident that the combined length of the undulations 26 and 27 could be made different from the combined length of the undulations 28 and 29, as described for example in connection with FIGURE 2, so as to obtain a difference in the magnitude of opening force required to remove the knock-out by a blow from one side as compared to the other side.

Referring now to FIGURE 5, there is shown a knockout structure which is a combination of FIGURES 2 and 4. In the structure of FIGURE 5, structure such as shown in FIGURE 2 has been made smaller, and structure such as shown in FIGURE 4 has been enlarged and encircles the other structure. It is to be understood that the FIGURE 4 structure could be reduced in size or the FIGURE 2 structure increased in size so as to reverse the position of the elements shown in FIGURE 5. It is also evident that the radius line 24 of FIGURE 3 could be transposed with the severance line 25 thereof and that a similar reversal may be provided in FIGURE 5.

Thus, FIGURE 5 includes a disc 30 surrounded by an annular member 31 having a set of undulations 3234 directed in one direction from the disc 30, and a second set of undulations 3537 directed and protruding in the opposite direction as described before. Thus also a second undulated annular means 38 is provided, the interior portion thereof in this embodiment comprising a flat annular member 39 surrounded by undulated annular means including the raised undulations 40, 41 and the depressed undulations 42, 43, each separated from the flat annular member portion 39 by a radius line 44 which encircles the same. It is evident that the combined length of the arcuate undulations 42 and 43 or 41 and 40 exceeds either set of internal undulations, whereby a sharp blow will remove either the disc 30 or the disc 30 and the annular member 31 as a unit depending upon the side of the sheet 11 from which the blow was delivered. Thereafter, a second blow delivered to either side of the annular member 30 will remove the same.

Referring to FIGURE 6, there is shown a structure which comprises the structure of FIGURE 2, within which or around which the structure of FIGURE 2 is again repeated so as to define lines of severance 45, 46, 47, and 48, in the sheet 11. The severance lines 45 and 46 thus define a first undulated annular member 49 within which there is disposed a disc 50, while the lines of severance 47 and 48 define a second undulated annular member 51 within which there is disposed a fiat annular member 52. In this embodiment, the disc 50 and the flat annular member 52 are preferably disposed in a coplanar relation with the sheet 11. A sharp blow delivered to a selected side of the disc 50 will selectively cause separation at one of the severance lines 45 and 46. Thereafter, a second blow delivered to a selected side of the annular member 52 will cause a further separation at a selected one of the severance lines 47 and 48. The structure of FIGURE 6 is otherwise similar to FIGURE 2, and the reader is referred to the foregoing description thereof for a more detailed description of FIGURE 6.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such embodiments as reasonably and 3,152,715 I 6 properly come within the scope of my contribution to 9. A knock-out structure in a sheet of material comthe art. prising:

I claim as my invention: (a) a disc disposed in substantially coplanar relation to l. A knock-out structure in a sheet of material comthe sheet; and prising: 5 (b) undulated annular means extending around said a disc having continuous undulated means at its disc, the undulations being defined at their outer peperiphery, some of the undulations protruding from riphery by one continuous press-fit severance line one side of the sheet, and other of the undulations through the thickness of said annular means, some protruding from the other side of the sheet. of the undulations protruding from one side of the 2. A knock-out structure in a sheet of material corn- 10 sheet, and other of the undulations protruding from prising: the other side of the sheet, said undulations each (a) a disc disposed in substantially coplanar relation to protruding by an amount less than the sheet thickthe sheet; and mess, each of said protruding undulations including a (b) undulated annular means extending continuously flat central portion extending parallel to the sheet around said disc, some of the undulations protrudand end portions each extending into the sheet and ing from one side of the sheet, and other of the integral with an end portion of an oppositely proundulations protruding from the other side of the truding adg'acent undulation.

sheet. 10. A knock-out structure in a sheet of material com- 3. A knock-out structure in a sheet of material comprising: prising: (a) a disc disposed in substantially coplanar relation to the sheet; and (b) an undulated annular member defined by two radi- (a) a disc; and (b) undulated annular means extending around said disc, the undulations being defined peripherallyby at least one continuous press-fit severance line through ally spaced press-fit continuous lines of severance extending around said disc, some of the undulations the thickness of said annular means, some of the unprotruding from one side of the sheet, and other of dulations protruding from one side of the sheet, and the undulations protruding from the other side of t other of the undulations protruding from the other the sheet, said undulations each protruding by an side of the sheet. amount less than the sheet thickness, each of said 4. A knock-out structure in a sheet of material comprotruding undulations including a flat central porprising: tion extending parallel to the sheet and end portions (:1) a disc; and each extending into the sheet and integral with an (b) undulated annular means extending around said end portion of an oppositely protruding adjacent disc, the undulations being defined at their outer peundulation, said undulations protruding from said riphery by one continuous press-fit severance line one side having a combined arcuate length substanthrough the thickness of said annular means, some of tially different from that of said other undulations the undulations protruding from one side of the sheet, protruding from said other side. and other of the undulations protruding from the 11. A knock-out structure in a sheet of material comother side of the sheet. prising:

5. A knock-out structure in a sheet of material comprising:

(a) a disc; and

(b) undulated annular means extending continuously (a) a disc;

(b) a substantially fiat annular member encircling said disc and radially spaced therefrom; and

(0) two undulated annular means encircling said disc,

around said disc, said undulations each protruding by an amount less than the sheet thickness.

and respectively disposed at the inner and outer peripheries of said flat annular member and being 6. A knock-out structure in a sheet of material comdefined by at least three radially spaced lines of prising: severance, some of the undulations in each of said i (a) a disc; and means protruding partially from one side of the j (b) undulated annular means extending around said sheet and the other of the undulations protruding l s Some f th nd lati ns protruding fr m n partially from the other side of the sheet; said un- Side of the Sheet, and other of the undulations P dulations in one of said means protruding from said truding from the other side of the sheet, each of said protruding undulations including a flat central portion extending parallel to the sheet, and end portions one side, the similarly directed undulation in the other of said means, and the oppositely directed undulations in said other of said means respectively each extending into the sheet and integral with an end h i b t ti ll diff t o bined arcuate portion of an oppositely protruding adjacent undulalengths. tion. 12. A knock-out structure in a sheet of material com- 7. A knock-out structure in a sheet of material comprising; pr1s1ng: (a) a disc;

a disc; and (b) a substantially fiat annular member encircling (b) a continuously undulated annular member defined truding from the other side of the sheet, said undulations protruding from said one side having a combined arcuate length substantially diiferent from that of said other undulations protruding from said other side.

0 said disc and radially spaced therefrom; and by radlally Spaced lmes of severange extendmg (c) two undulated annular means encircling said disc, I around said disc, some of the undulations protrud and respectively disposed [at the inner and Outer ing from one side of the sheet, and other of the uneripheries of said flat annular member and bein dulations protruding from the other side of the sheet. gefined y four radially spaced lines of severanceg r g knock-out structure m a Sheet of matenal comsome of the undulations in each of said means pro p di d truding partially from one side of the sheet and the (b) undulated annular means extending around said other of h undulations protruding p i lf from disc, some of the undulatio t di f one the other s1de of the sheet; said undulations in one side of the sheet, and other of the undulations pro-- of said means protruding from said one Side, the

oppositely directed undulations in said one of said means, the similarly directed undulations in the other of said means, and the oppositely directed undulations in said other of said means respectively having substantially different combined arcuate lengths.

13. A knock-out structure in a sheet of material comprising:

(a)- a'disc; and

(b) two undulated annular means encircling said disc, and arranged concentrically with each other and being defined by at least three radially spaced lines of severance, some of the undulations in each of said means protruding partially from one side of the sheet and the other of the undulations protruding partially from the other side of the sheet; said undulations in one of said means protruding from said one side, the similarly directed undulations in the other of said means, and the oppositely directed undulations in said other of said means respectively having substantially different combined arcuate lengths.

aperture with a drive fit, With-the undulations thereof alternately projecting from both sides of the sheet; and

(c) a central slug having an outer dimension larger than the opening in said annular slug and disposed therein with a drive fit, coplanar with said sheet.

References Cited in the file of this patent UNITED STATES- PATENTS Appleton Feb. 11, 1913 Wuensch Sept. 4, 1917 

14. A KNOCK-OUT STRUCTURE IN A SHEET OF MATERIAL, COMPRISING: (A) MEANS DEFINING AN APERTURE IN THE SHEET; (B) AN UNDULATED ANNULAR SLUG HAVING AN OUTER DIMENSION LARGER THAN SAID APERTURE AND DISPOSED IN SAID APERTURE WITH A DRIVE FIT, WITH THE UNDULATIONS THEREOF ALTERNATELY PROJECTING FROM BOTH SIDES OF THE SHEET; AND (C) A CENTRAL SLUG HAVING AN OUTER DIMENSION LARGER THAN THE OPENING IN SAID ANNULAR SLUG AND DISPOSED THEREIN WITH A DRIVE FIT, COPLANAR WITH SAID SHEET. 